Preparation Stationary Sample Holders This presentation gives a description of the preparation of powder samples in PW1172/01 sample holders according to the backloading technique. The preparation of samples for analysis is of critical importance if accurate and fast results are to be obtained, and the procedures detailed in this section should be careful followed. Additionally, the introduction of errors, such as contamination, material loss, alteration of composition, especially of the sample surface, and change of lattice type, during the course of sample preparation, and afterwards, should be avoided. Contamination of the sample can be caused by dust, material from a previous sample which remained in the sample preparation equipment, or by material from the sample preparation equipment resulting from abrasion. Material loss is attributed to non-quantitative transfer in concentration determining operations (dilution, binder addition), loss of a small fraction of particle size as dust, and material remaining in the sample preparation equipment. Alteration of composition is attributed to losses of material particles which are of different composition to the average composition. For example, magnetic particles, fine dust, and volatile substances. Also, physical or chemical alteration; that is, by decomposition during preparation, such as oxidation, loss of combined water or carbon dioxide by overheating and pick-up of water or carbon dioxide from the air, or by the addition of materials of different composition such as by contamination. Change of lattice type; that is, transition to another phase, is attributed to pressure, temperature, or a combination of the two. The sample surface is only measured up to a depth of 1 or 2 mm in some cases, but in most cases only a hundred microns or even less. Typical examples of errors which can occur here are non-representativeness (sample surface has different composition than the average composition) caused by segregation, adhering particles or extracted particles, smearing and bad particle statistics, non-uniformity (sample surface is not equal for all samples) such as non-flat samples (concave or convex), or differences in surface roughness. Most of the errors can be avoided if samples are prepared carefully with cleaned equipment in a clean room. Once samples have been prepared they must be stored in a dust-free environment such as desiccators sometimes under vacuum or filled with moisture absorbers like Silica gel. If samples are difficult to handle, use pincers or gloves. Samples for X-ray analysis should be, in effect, infinitely thick, depending on the energy of the X-ray line and the matrix of the samples. Usually a 2 to 3 mm thickness seems to be sufficient. Once the sample has been prepared, care should be taken that it fits into the holder properly. To achieve a sufficient sample strength during sample preparation, the sample must be ground very fine, achieving an average grain size of 5 mm, with a maximum grain size of 25 mm. If both hard and soft materials are present together, the required size reduction of particles might be achieved by pressing the sample instead of grinding. This may prevent the softer material being ground by the harder one.

PW1172 Flat Sample Holder PW1172/01 The PW1172/01 (set of 25) sample holders are aluminum holders for powder samples with a volume of 15 mm x 20 mm x 1.8 mm available for use with X’Pert PRO systems without a spinner, but with a PW3071/60 Bracket stage for flat samples or with a PW3074/00 Multi-purpose sample stage. One back plate per sample holder is included, allowing the back-loading technique to be employed in this type of sample holders. Application General powder analysis. Powders, with a particle size less than 25 mm and a small or average density, can usually be analyzed without a binder.

Sample Preparation Equipment Sample preparation equipment used to prepare specimen for the PW1172/01 sample holders comprises: A cover glass A mortar and pestle A Stanley knife blade Adhesive tape.

Preparing a Stationary Sample (1) The Sample Holder mounted onto a Preparation Glass Cover To prepare a powder sample in a PW1172/01 sample holder, proceed as follows: 1: Use self-adhesive tape to secure a glass plate to the front side of the sample holder

Preparing a Stationary Sample (2) The Powder is spread in the Flat Sample Holder 2: Spread the powder in the holder.

Preparing a Stationary Sample (3) The Powder is pressed using a Preparation Glass Cover 3: Use a microscope glass to press in the powder.

Preparing a Stationary Sample (4) Removal of Surplus Powder with a Knife Blade 4: Remove the surplus of powder above the rim of the holder with a Stanley knife or glass plate.

Preparing a Stationary Sample (5) The Back Cover is clamped onto the Flat Sample Holder 5: Secure the back cover to the holder.

Preparing a Stationary Sample (6) The Powder Sample ready to use 6: Turn the sample holder upside down and remove the glass cover. A smooth, flat sample surface, flush with the sample holder ring surface is shown. The sample is now ready for use. NOTE: To protect the sample, the front glass plate should not be removed before measuring. NOTE: Insert the sample into the sample stage (PW3071/60 or PW3074/60) only until the sample material is just free from the reference plane of the sample stage. If you push it any further the sample material could be contaminated with that of previous samples and Al lines from the sample holder may appear in your diffractogram.

Mounting a Flat Solid Sample Irregular shaped flat samples, pressed pellets or other small solid samples may also be mounted onto the PW1172/01 sample holder. A small amount of plasticine or modeling wax can be used to hold the sample in place.